linux-kernel - Re: xen: Fix possible page fault in fifo events

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Message-ID: <53D64828.6020209@citrix.com>
Date:	Mon, 28 Jul 2014 13:55:04 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Frediano Ziglio <frediano.ziglio@...rix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
CC:	xen-devel <xen-devel@...ts.xenproject.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: xen: Fix possible page fault in fifo events

On 15/07/14 14:48, Frediano Ziglio wrote:
> sync_test_bit function require a long* read access to pointer.
> This is a problem if the you are using last entry in the page causing
> an access to next page. If this page is not readable you get a memory
> access failure (page fault).
> All other x64 bit functions access memory using 32 bit operations.
> For processors different than x64 long aligned operations are used.

I think we should implement a set of 32-bit bit ops.  We fudged around
it for the arm64 problem but this second problem shows we need a better
solution.

David

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